Messages in this thread | | | Subject | Re: [PATCH v3 02/12] iommu: Add iommu_split_block interface | From | Lu Baolu <> | Date | Wed, 14 Apr 2021 15:14:32 +0800 |
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On 4/13/21 4:54 PM, Keqian Zhu wrote: > Block(largepage) mapping is not a proper granule for dirty log tracking. > Take an extreme example, if DMA writes one byte, under 1G mapping, the > dirty amount reported is 1G, but under 4K mapping, the dirty amount is > just 4K. > > This adds a new interface named iommu_split_block in IOMMU base layer. > A specific IOMMU driver can invoke it during start dirty log. If so, the > driver also need to realize the split_block iommu ops. > > We flush all iotlbs after the whole procedure is completed to ease the > pressure of IOMMU, as we will hanle a huge range of mapping in general. > > Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com> > Signed-off-by: Kunkun Jiang <jiangkunkun@huawei.com> > --- > drivers/iommu/iommu.c | 41 +++++++++++++++++++++++++++++++++++++++++ > include/linux/iommu.h | 11 +++++++++++ > 2 files changed, 52 insertions(+) > > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c > index 667b2d6d2fc0..bb413a927870 100644 > --- a/drivers/iommu/iommu.c > +++ b/drivers/iommu/iommu.c > @@ -2721,6 +2721,47 @@ int iommu_domain_set_attr(struct iommu_domain *domain, > } > EXPORT_SYMBOL_GPL(iommu_domain_set_attr); > > +int iommu_split_block(struct iommu_domain *domain, unsigned long iova, > + size_t size) > +{ > + const struct iommu_ops *ops = domain->ops; > + unsigned int min_pagesz; > + size_t pgsize; > + bool flush = false; > + int ret = 0; > + > + if (unlikely(!ops || !ops->split_block)) > + return -ENODEV; > + > + min_pagesz = 1 << __ffs(domain->pgsize_bitmap); > + if (!IS_ALIGNED(iova | size, min_pagesz)) { > + pr_err("unaligned: iova 0x%lx size 0x%zx min_pagesz 0x%x\n", > + iova, size, min_pagesz); > + return -EINVAL; > + } > + > + while (size) { > + flush = true; > + > + pgsize = iommu_pgsize(domain, iova, size); > + > + ret = ops->split_block(domain, iova, pgsize); > + if (ret) > + break; > + > + pr_debug("split handled: iova 0x%lx size 0x%zx\n", iova, pgsize); > + > + iova += pgsize; > + size -= pgsize; > + } > + > + if (flush) > + iommu_flush_iotlb_all(domain); > + > + return ret; > +} > +EXPORT_SYMBOL_GPL(iommu_split_block);
Do you really have any consumers of this interface other than the dirty bit tracking? If not, I don't suggest to make this as a generic IOMMU interface.
There is an implicit requirement for such interfaces. The iommu_map/unmap(iova, size) shouldn't be called at the same time. Currently there's no such sanity check in the iommu core. A poorly written driver could mess up the kernel by misusing this interface.
This also applies to iommu_merge_page().
Best regards, baolu
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